Question: Simplify the following expression: $x = \dfrac{5}{6r} - \dfrac{1}{7r}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $6r$ and $7r$ $\lcm(6r, 7r) = 42r$ $ x = \dfrac{7}{7} \cdot \dfrac{5}{6r} - \dfrac{6}{6} \cdot \dfrac{1}{7r} $ $x = \dfrac{35}{42r} - \dfrac{6}{42r}$ $x = \dfrac{35 -6}{42r}$ $x = \dfrac{29}{42r}$